Whether you’re a Pygmy in the Congolese rainforest or a big-city hipster, certain aspects of music will touch you in the same ways—but others very differently, a study suggests.

“People have been trying to figure out for quite a while whether the way that we react to music is based on the culture that we come from or on some universal features of the music itself,” said co-researcher Stephen McAdams of McGill University in Montreal. “Now we know that it is actually a bit of both.”

The researchers traveled deep into the rainforest to play music to a very isolated people, the Mbenzélé Pygmies, who live without radio, television or electricity. They then compared how the Mbenzélé responded both to their own and to unfamiliar Western music, with how Canadians in downtown Montreal responded to the same pieces.

They found that the two groups were similar in their responses to how exciting or calming they found the music to be—but differed regarding whether specific pieces made them feel good or bad. The Pygmies tended to rate everything, even “scary” music, as making them happy, according to the study, published in the research journal Frontiers in Psychology.

The investigators played 19 short musical extracts (11 western and 8 Pygmy) of between about 30 and 90 seconds to 40 Pygmies and an equal number of Canadians. Because all the Mbenzélé Pygmies sing regularly for ceremonial purposes, the Canadians recruited for the study were all either amateur or professional musicians.

The Western music was designed to induce a range of emotions from calm to excited, and from happy to anxious or sad, and included both orchestral music and excerpts from three popular films (Psycho, Star Wars, and Schindler’s List).

The Pygmy pieces were all polyphonic (multiple-voiced) vocal pieces that are fairly upbeat and tend to be performed in ceremonial contexts to calm anger, or express comfort after a death, for example, or to bid good fortune before a hunting expedition leaves the village, or even to pacify a crying child.

The researchers used emoticons with smiling or frowning faces at each end of a continuum to get people to identify whether the music made them feel good or bad. They also asked participants to rate whether the music made them feel calm (close-eyed emoticon) or excited (open-eyed face). As participants listened, various measurements were also taken such as heart rate, rate of respiration, and amount of sweat on the palms.

“Our major discovery is that listeners from very different groups both responded to how exciting or calming they felt the music to be in similar ways,” said Hauke Egermann of the Technische Universität in Berlin, who did part of the research while at McGill University in Montreal. “This is probably due to certain low-level aspects of music such as tempo (or beat), pitch (how high or low the music is on the scale) and timbre (tone color or quality), but this will need further research.”

The main difference between Pygmy and Canadian listeners, the researchers said, was that the Canadians described themselves as feeling a much wider range of emotions as they listened to the Western music than the Pygmies felt when listening to either their own or Western music. This is probably attributable to the varying roles that music plays in each culture.

“Negative emotions are felt to disturb the harmony of the forest in Pygmy culture and are therefore dangerous,” said Nathalie Fernando of the University of Montreal’s Faculty of Music, who has been collecting and documenting Mbenzélé music-making for 10 years. “If a baby is crying, the Mbenzélé will sing a happy song. If the men are scared of going hunting, they will sing a happy song—in general music is used in this culture to evacuate all negative emotions, so it is not really surprising that the Mbenzélé feel that all the music they hear makes them feel good.”

A whale that can live over 200 years with little evidence of age-related disease may provide untapped insights into how to live a long and healthy life, biologists say.

In the Jan. 6 issue of the research journal Cell Reports, scientists present the bowhead whale’s complete genome and identify what they say are key differences with other mammals.

Changes in bowhead genes related to cell division, DNA repair, cancer, and aging may have helped increase its longevity and cancer resistance, according to the researchers.

“Our understanding of species’ differences in longevity is very poor, and thus our findings provide novel candidate genes for future studies,” said the study’s senior author, João Pedro de Magalhães of the University of Liverpool in the UK.

“My view is that species evolved different ‘tricks’ to have a longer lifespan, and by discovering the ‘tricks’ used by the bowhead we may be able to apply those findings to humans in order to fight age-related diseases.”

Also, he added, large whales with over 1,000 times more cells than humans don’t seem to have higher cancer risk, suggesting the whales have natural mechanisms that help suppress cancer.

Magalhães and his team plan to breed mice with various bowhead genes in hopes of determining the importance of different genes for longevity and resistance to diseases. They also note that because the bowhead’s genome is the first among large whales to be decoded, the new information may help reveal physiological adaptations related to large size.

Meteorite hunters plucked a Martian rock from an Antarctic ice field 30 years ago. A new research on that rock, this month reveals a record of the planet’s climate billions of years ago, back when water likely washed across its surface and any life that ever formed there might have emerged.

Scientists from the University of California, San Diego, NASA and the Smithsonian Institution report detailed measurements of minerals within the meteorite in the early online edition of the Proceedings of the National Academy of Sciences this week.

“Minerals within the meteorite hold a snapshot of the planet’s ancient chemistry, of interactions between water and atmosphere,” said Robina Shaheen, the lead author of the report.

The unlovely stone, which fell to Earth 13 thousand years ago, looked a lot like a potato and has quite a history. Designated ALH84001, it is the oldest meteorite we have from Mars, a chunk of solidified magma from a volcano that erupted four billion years ago. Since then something liquid, probably water, seeped through pores in the rock and deposited globules of carbonates and other minerals.

The carbonates vary subtly depending on the sources of their carbon and oxygen atoms. Both carbon and oxygen occur in heavier and lighter versions, or isotopes. The relative abundances of isotopes forms a chemical signature that careful analysis and sensitive measurements can uncover.

Mars’s atmosphere is mostly carbon dioxide but contains some ozone. The balance of oxygen isotopes within ozone are strikingly weird with enrichment of heavy isotopes through a physical chemical phenomenon first described by co-author Mark Thiemens, a professor of chemistry at UC San Diego, and colleagues 25 years ago.

“When ozone reacts with carbon dioxide in the atmosphere, it transfers its isotopic weirdness to the new molecule,” said Shaheen, who investigated this process of oxygen isotope exchange as a graduate student at the University of Heidelberg in Germany. When carbon dioxide reacts with water to make carbonates, the isotopic signature continues to be preserved.

The degree of isotopic weirdness in the carbonates reflects how much water and ozone was present when they formed. It’s a record of climate 3.9 billion years ago, locked in a stable mineral. The more water, the smaller the weird ozone signal.

This team measured a pronounced ozone signal in the carbonates within the meteorite, suggesting that although Mars had water back then, vast oceans were unlikely. Instead, the early Martian landscape probably held smaller seas.

“What’s also new is our simultaneous measurements of carbon isotopes on the same samples. The mix of carbon isotopes suggest that the different minerals within the meteorite had separate origins,” Shaheen said. “They tell us the story of the chemical and isotopic compositions of the atmospheric carbon dioxide.”

ALH84001 held tiny tubes of carbonate that some scientists saw as potential evidence of microbial life, though a biological origin for the structures has been discarded. On December 16, NASA announced another potential whiff of Martian life in the form of methane sniffed by the rover Curiosity.

Carbonates can be deposited by living things that scavenge the minerals to build their skeletons, but that is not the case for the minerals measured by this team. “The carbonate we see is not from living things,” Shaheen said. “It has anomalous oxygen isotopes that tell us this carbonate is abiotic.”

By measuring the isotopes in multiple ways, the chemists found carbonates depleted in carbon-13 and enriched in oxygen-18. That is, Mars’s atmosphere in this era, a period of great bombardment, had much less carbon-13 than it does today.

The change in relative abundances of carbon and oxygen isotopes may have occurred through extensive loss of Martian atmosphere. A thicker atmosphere would likely have been required for liquid water to flow on the planet’s chilly surface.

“We now have a much deeper and specific insight into the earliest oxygen-water system in the solar system,” Thiemens said. “The question that remains is when did planets, Earth and Mars, get water, and in the case of Mars, where did it go? We’ve made great progress, but still deep mysteries remain.”

Scheduled for launch on Jan. 29, 2015, NASA’s Soil Moisture Active Passive (SMAP) instrument will measure the moisture lodged in Earth’s soils with an unprecedented accuracy and resolution. The instrument’s three main parts are a radar, a radiometer and the largest rotating mesh antenna ever deployed in space.

Remote sensing instruments are called “active” when they emit their own signals and “passive” when they record signals that already exist. The mission’s science instrument ropes together a sensor of each type to corral the highest-resolution, most accurate measurements ever made of soil moisture — a tiny fraction of Earth’s water that has a disproportionately large effect on weather and agriculture.

To enable the mission to meet its accuracy needs while covering the globe every three days or less, SMAP engineers at NASA’s Jet Propulsion Laboratory in Pasadena, California, designed and built the largest rotating antenna that could be stowed into a space of only one foot by four feet (30 by 120 centimeters) for launch. The dish is 19.7 feet (6 meters) in diameter.

“We call it the spinning lasso,” said Wendy Edelstein of NASA’s Jet Propulsion Laboratory, Pasadena, California, the SMAP instrument manager. Like the cowboy’s lariat, the antenna is attached on one side to an arm with a crook in its elbow. It spins around the arm at about 14 revolutions per minute (one complete rotation every four seconds). The antenna dish was provided by Northrop Grumman Astro Aerospace in Carpinteria, California. The motor that spins the antenna was provided by the Boeing Company in El Segundo, California.

“The antenna caused us a lot of angst, no doubt about it,” Edelstein noted. Although the antenna must fit during launch into a space not much bigger than a tall kitchen trash can, it must unfold so precisely that the surface shape of the mesh is accurate within about an eighth of an inch (a few millimeters).

The mesh dish is edged with a ring of lightweight graphite supports that stretch apart like a baby gate when a single cable is pulled, drawing the mesh outward. “Making sure we don’t have snags, that the mesh doesn’t hang up on the supports and tear when it’s deploying — all of that requires very careful engineering,” Edelstein said. “We test, and we test, and we test some more. We have a very stable and robust system now.”

SMAP’s radar, developed and built at JPL, uses the antenna to transmit microwaves toward Earth and receive the signals that bounce back, called backscatter. The microwaves penetrate a few inches or more into the soil before they rebound. Changes in the electrical properties of the returning microwaves indicate changes in soil moisture, and also tell whether or not the soil is frozen. Using a complex technique called synthetic aperture radar processing, the radar can produce ultra-sharp images with a resolution of about half a mile to a mile and a half (one to three kilometers).

SMAP’s radiometer detects differences in Earth’s natural emissions of microwaves that are caused by water in soil. To address a problem that has seriously hampered earlier missions using this kind of instrument to study soil moisture, the radiometer designers at NASA’s Goddard Space Flight Center, Greenbelt, Maryland, developed and built one of the most sophisticated signal-processing systems ever created for such a scientific instrument.

The problem is radio frequency interference. The microwave wavelengths that SMAP uses are officially reserved for scientific use, but signals at nearby wavelengths that are used for air traffic control, cell phones and other purposes spill over into SMAP’s wavelengths unpredictably. Conventional signal processing averages data over a long time period, which means that even a short burst of interference skews the record for that whole period. The Goddard engineers devised a new way to delete only the small segments of actual interference, leaving much more of the observations untouched.

Combining the radar and radiometer signals allows scientists to take advantage of the strengths of both technologies while working around their weaknesses. “The radiometer provides more accurate soil moisture but a coarse resolution of about 40 kilometers [25 miles] across,” said JPL’s Eni Njoku, a research scientist with SMAP. “With the radar, you can create very high resolution, but it’s less accurate. To get both an accurate and a high-resolution measurement, we process the two signals together.”

SMAP will be the fifth NASA Earth science mission launched within the last 12 months.

Body cameras on police officers may reduce abusive behavior both by and against officers, a study has found.

Researchers from the University of Cambridge in the U.K. published the results of an experiment they conducted on the cameras’ effects in Rialto, Calif. in 2012. The year-long study found that use of force by camera-wearing police fell by 59 percent and reports against officers dropped by 87 percent against the previous year’s figures.

While the technology helps capture evidence for potential use in court, its greatest benefit may be preventing escalation to violence in the first place, the investigators said—in short, people tend to behave when they know they’re on camera.

However, the research team caution that the Rialto experiment is only a first step, and that more needs to be known about the impact of body-worn cameras before police departments are pressured into adopting the technology.

Vital questions remain, they explained, about how routine provision of digital video as evidence will affect prosecution expectations, and the storage technology and policies that the immense amounts of new data will require. President Obama recently promised to spend $75 million of federal funds on body-worn-video to address persistent protests over police killing unarmed black men.

Some question the merit of camera technology given that the officer responsible for killing Eric Garner—a 43-year-old black man suffocated during arrest for selling untaxed cigarettes—was acquitted by a grand jury even though a bystander filmed the altercation on a cell phone. Footage showed an illegal ‘chokehold’ placed on Garner who repeatedly states: “I can’t breathe.” (A medical examiner ruled the death a homicide).

For the Cambridge researchers, the Rialto results show that body-worn-cameras can reduce the need for such evidence by preventing excessive force in the first place.

“In the tragic case of Eric Garner, police weren’t aware of the camera and didn’t have to tell the suspect that he, and therefore they, were being filmed,” said Barak Ariel of Cambridge’s Institute of Criminology, who conducted the experiment with Cambridge colleague Alex Sutherland and Rialto police chief Tony Farrar.

“With institutional body-worn-camera use, an officer is obliged to issue a warning from the start that an encounter is being filmed, impacting the psyche of all involved by conveying a straightforward, pragmatic message: we are all being watched, videotaped and expected to follow the rules,” he said.

The idea behind body-worn-video, in which small high-definition cameras are strapped to a police officers’ torso or hat, is that every step of every police-public interaction—from the mundane to those involving deadly force—gets recorded to capture the closest approximation of actual events for evidence purposes, with only case-relevant data being stored.

In Rialto, police shifts over the course of a year were randomly assigned to be either with or without camera, with video covering over 50,000 hours of interactions. Ariel and colleagues are replicating the Rialto experiment with over 30 forces across the world, and early signs match the Rialto success, Ariel said.

Body-worn cameras seem very cost-effective: analysis from Rialto showed every dollar spent on the technology saved about four dollars on complaints litigations, the researchers added. But with technology becoming cheaper, the sheer volumes of data storage could become crippling.

And, if body-worn cameras become the norm, what might the cost be when video evidence isn’t available? “Historically, courtroom testimonies of response officers have carried tremendous weight, but prevalence of video might lead to reluctance to prosecute when there is no evidence from body-worn-cameras to corroborate the testimony of an officer, or even a victim,” said Ariel.

New UCLA research indicates that lost memories can be restored. It shows some rays of hope for patients in the early stages of Alzheimer’s disease.

For decades, most neuroscientists have believed that memories are stored at the synapses — the connections between brain cells, or neurons — which are destroyed by Alzheimer’s disease. The new study provides evidence contradicting this idea.

“Long-term memory is not stored at the synapse,” said David Glanzman, a senior author of the study, and a UCLA professor of integrative biology and physiology and of neurobiology. “That’s a radical idea, but that’s where the evidence leads. The nervous system appears to be able to regenerate lost synaptic connections. If you can restore the synaptic connections, the memory will come back. It won’t be easy, but I believe it’s possible.” The findings were published recently in eLife.

Glanzman’s research team studies a type of marine snail called Aplysia to understand the animal’s learning and memory. The Aplysia displays a defensive response to protect its gill from potential harm, and the researchers are especially interested in its withdrawal reflex and the sensory and motor neurons that produce it.

They enhanced the snail’s withdrawal reflex by giving it several mild electrical shocks on its tail. The enhancement lasts for days after a series of electrical shocks, which indicates the snail’s long-term memory. Glanzman explained that the shock causes the hormone serotonin to be released in the snail’s central nervous system.

Long-term memory is a function of the growth of new synaptic connections caused by the serotonin, said Glanzman, a member of UCLA’s Brain Research Institute. As long-term memories are formed, the brain creates new proteins that are involved in making new synapses. If that process is disrupted — for example by a concussion or other injury — the proteins may not be synthesized and long-term memories cannot form. (This is why people cannot remember what happened moments before a concussion.)

“If you train an animal on a task, inhibit its ability to produce proteins immediately after training, and then test it 24 hours later, the animal doesn’t remember the training,” Glanzman said. “However, if you train an animal, wait 24 hours, and then inject a protein synthesis inhibitor in its brain, the animal shows perfectly good memory 24 hours later. In other words, once memories are formed, if you temporarily disrupt protein synthesis, it doesn’t affect long-term memory. That’s true in the Aplysia and in human’s brains.” (This explains why people’s older memories typically survive following a concussion.)

Glanzman’s team found the same mechanism held true when studying the snail’s neurons in a Petri dish. The researchers placed the sensory and motor neurons that mediate the snail’s withdrawal reflex in a Petri dish, where the neurons re-formed the synaptic connections that existed when the neurons were inside the snail’s body. When serotonin was added to the dish, new synaptic connections formed between the sensory and motor neurons. But if the addition of serotonin was immediately followed by the addition of a substance that inhibits protein synthesis, the new synaptic growth was blocked; long-term memory could not be formed.

The researchers also wanted to understand whether synapses disappeared when memories did. To find out, they counted the number of synapses in the dish and then, 24 hours later, added a protein synthesis inhibitor. One day later, they re-counted the synapses.

What they found was that new synapses had grown and the synaptic connections between the neurons had been strengthened; late treatment with the protein synthesis inhibitor did not disrupt the long-term memory. The phenomenon is extremely similar to what happens in the snail’s nervous system during this type of simple learning, Glanzman said.

Next, the scientists added serotonin to a Petri dish containing a sensory neuron and motor neuron, waited 24 hours, and then added another brief pulse of serotonin — which served to remind the neurons of the original training — and immediately afterward add the protein synthesis inhibitor. This time, they found that synaptic growth and memory were erased. When they re-counted the synapses, they found that the number had reset to the number before the training, Glanzman said. This suggests that the “reminder” pulse of serotonin triggered a new round of memory consolidation, and that inhibiting protein synthesis during this “reconsolidation” erased the memory in the neurons.

If the prevailing wisdom were true — that memories are stored in the synapses — the researchers should have found that the lost synapses were the same ones that had grown in response to the serotonin. But that’s not what happened: Instead, they found that some of the new synapses were still present and some were gone, and that some of the original ones were gone, too.

Glanzman said there was no obvious pattern to which synapses stayed and which disappeared, which implied that memory is not stored in synapses.

When the scientists repeated the experiment in the snail, and then gave the animal a modest number of tail shocks — which do not produce long-term memory in a naive snail — the memory they thought had been completely erased returned. This implies that synaptic connections that were lost were apparently restored.

“That suggests that the memory is not in the synapses but somewhere else,” Glanzman said. “We think it’s in the nucleus of the neurons. We haven’t proved that, though.”

Glanzman said the research could have significant implications for people with Alzheimer’s disease. Specifically, just because the disease is known to destroy synapses in the brain doesn’t mean that memories are destroyed.

“As long as the neurons are still alive, the memory will still be there, which means you may be able to recover some of the lost memories in the early stages of Alzheimer’s,” he said.

Glanzman added that in the later stages of the disease, neurons die, which likely means that the memories cannot be recovered.

The cellular and molecular processes seem to be very similar between the marine snail and humans, even though the snail has approximately 20,000 neurons and humans have about 1 trillion.

Almost all the processes that are involved in memory in the snail also have been shown to be involved in memory in the brains of mammals, Glanzman said.

Glanzman’s demonstration that the NMDA receptor plays a critical role in learning in a simple animal like the marine snail was entirely unexpected at the time.

Crows can reason by analogy, a study has found, showing an ability to recognize how different pairs of objects have similar relationships.

That means crows join humans, apes and monkeys in showing advanced “relational” thinking, according to the research. The crows also passed their test without training, except on a similar-but-easier task, the researchers said.

The crows’ feat is “phenomenal,” said Ed Wasserman, a University of Iowa psychologist and co-author of a report on the findings, though “it’s been done before with apes and monkeys.” Wasserman added that the crow brain is as “as special to birds as the brain of an ape is special to mammals.”

In the paper, published by Dec. 18 in the journal Current Biology, Wasserman and researchers at Lomonosov Moscow State University describe how they initially trained two hooded crows to win treats by matching pictures.

Later, they presented the birds with two cups, one empty and one with a treat. Each cup was covered with a card showing two pictures. The task was to choose the card where the pictured objects had the same relationship as those shown on a third, “sample” card.

For example, if the sample card displayed two same-sized squares, the crows might have to choose the card with two same-sized circles, rather than two different-sized circles.

The investigators said they were surprised to find that the crows could correctly perform this without specific training. Their previous game had involved exactly matching pictures rather than analogies.

“Honestly, if it was only by brute force that the crows showed this learning, then it would have been an impressive result. But this feat was spontaneous,” Wasserman said, although some background knowledge was present.

Anthony Wright, a neurobiologist at the University of Texas-Houston Medical School, said the discovery is on par with demonstrations of tool use by some birds, including crows.

“Analogical reasoning, matching relations to relations, has been considered to be among the more so-called ‘higher order’ abstract reasoning processes,” he said. “For decades such reasoning has been thought to be limited to humans and some great apes. The apparent spontaneity of this finding makes it all the more remarkable.”

Joel Fagot, director of research at the University of Aix-Marseille in France, agreed the results shatter the notion that “sophisticated forms of cognition can only be found in our ‘smart’ human species. Accumulated evidence suggests that animals can do more than expected.”

Wasserman concedes there will be skeptics and hopes the experiment will be repeated with more crows as well as other species. He suspects researchers will have more such surprises in store for science. “We have always sold animals short,” he said. “That human arrogance still permeates contemporary cognitive science.”

Here’s a nice surprise: quantum physics is less complicated than we thought, according to new research. The work links two strange features of the quantum world—or nature at the smallest scales, such as that of subatomic particles—calling them different manifestations of the same thing.

These features go by the names “wave-particle duality” and the “uncertainty principle.” In work published Dec. 19 in the journal Nature Communications, the researchers, who did the work at the National University of Singapore, say the first is just the second in disguise.

The connection “comes out very naturally when you consider them as questions about what information you can gain about a system,” said one of the scientists, Stephanie Wehner, who is now at the Delft University of Technology in the Netherlands.

Wave-particle duality is the idea that a quantum object can behave like a wave, but that the wave behavior stops if you try to locate the object.

The duality is seen in experiments in which subatomic particles, such as electrons, are fired one by one at a screen with two thin slits. The particles pile up behind the slits not in two heaps, but in a striped pattern as you’d expect for waves that “interfere” with each other. An everyday example of wave interference occurs when you toss two pebbles in a pond at once a small distance away from each other: when the two sets of ripples meet, they form characteristic patterns as their effects add up.

However, in the quantum case, the pattern vanishes if you sneak a look at which slit a particle goes through—at which point the particles start to act like particles and not waves.

The quantum uncertainty principle is the idea that it’s impossible to know certain pairs of things about a quantum particle at once. For example, the more precisely you know the position of an atom, the less precisely you can know its speed. It’s a limit on the fundamental knowability of nature, not a statement on measurement skill. The new work finds that there is an identical sort of limit on how much you can learn about a system’s wave versus the particle behavior.

Wave-particle duality and uncertainty have been fundamental concepts in quantum physics since the early 1900s. “We were guided by a gut feeling, and only a gut feeling, that there should be a connection,” said co-researcher Patrick Coles, who is now at the Institute for Quantum Computing in Waterloo, Canada.

One can write equations that capture how much can be learned about pairs of properties subject to the uncertainty principle. Coles, Wehner and co-author Jedrzej Kaniewski work with a form of such equations known as “entropic uncertainty relations,” and they found that all the maths previously used to describe wave-particle duality could be reformulated in terms of these relations.

“It was like we had discovered the ‘Rosetta Stone’ that connected two different languages,” said Coles. “The literature on wave-particle duality was like hieroglyph that we could now translate into our native tongue.”

Because the entropic uncertainty relations used in their translation have also been used in demonstrating the security of quantum cryptography—schemes for secure communication using quantum particles—the researchers suggest the work could help inspire new cryptography methods.

In earlier papers, Wehner and collaborators found connections between the uncertainty principle and other aspects of physics, namely quantum “non-locality” and the second law of thermodynamics. The first deals with particles’ ability to act as though they can communicate instantaneously over long distances; the second states that disorder in the universe can always increase but not decrease. The researchers say their next goal is to think about how all this fits into a bigger picture of how nature works.

The dinosaurs’ extinction 66 million years ago is thought to have opened the way for mammals to dominate the land. But a new study claims many of them died off too.

“If a few lucky species didn’t make it through, then mammals may have gone the way of the dinosaurs and we wouldn’t be here,” said Steve Brusatte of the University of Edinburgh in the U.K., one of the authors of a report on the findings.

Among mammals, the study argues, the brunt of the disaster seems to have hit a group known as metatherians—extinct relatives of living marsupials (“mammals with pouches,” such as opossums and kangaroos.) These thrived in the shadow of the dinosaurs during the Cretaceous period, just before the extinction.

The study, published in the research journal Zookeys, finds these once-abundant mammals nearly followed the dinosaurs into oblivion.

When a 10-km (6-mile)-wide asteroid struck what is now Mexico, unleashing a global cataclysm, some two-thirds of all metatherians living in North America perished, according to the researchers. These casualties, they said, included more than 90 percent of species living in the northern Great Plains, the best area in the world for preserving latest Cretaceous mammal fossils.

Metatherians, the scientists added, would never recover their previous diversity, which is why marsupials are rare today and largely restricted to areas in Australia and South America. Taking advantage of the metatherian demise were the placental mammals: species that give live birth to well-developed young. They are almost everywhere today and include everything from mice to men.

“It wasn’t only that dinosaurs died out, providing an opportunity for mammals to reign, but that many types of mammals, such as most metatherians, died out too—this allowed advanced placental mammals to rise to dominance,” said Thomas Williamson of the New Mexico Museum of Natural History and Science, lead author of the paper.

The study reviews the Cretaceous evolutionary history of metatherians and provides a family tree for these mammals based on the latest fossil records, which researchers said allowed them to study extinction patterns in unprecedented detail.

Levels of the organic gas methane are periodically spiking at the Gale Crater on Mars—suggesting something, possibly something alive, is creating the substance, scientists say.

Most of Earth’s methane production has a biological origin, but there are other ways methane, the simplest organic molecule, can arise naturally. Organic molecules are carbon-based and are essential ingredients for life.

The new findings, from the NASA Mars rover Curiosity, are published this week in the research journal Science.

Investigators said the findings suggest that the methane level in Mars’ atmosphere at the 154-km (96 mile) wide crater is generally lower than models predict, but that it spikes often. This implies the gas arises periodically from some nearby source, they added.

The scientists, from the NASA Jet Propulsion Laboratory in Pasadena, Calif. and other institutions, used 20 months of data collected by instruments on Curiosity to gauge levels of the gas at crater, near where the rover landed.

Their study found that the stable, background level of atmospheric methane is less than half of what was expected from known processes, such as the light-induced breakdown of dust and organic materials delivered to Mars by meteorites.

However, the researchers also found that this background level of methane spiked about tenfold, sometimes over the course of just 60 Martian days, which was surprising because the gas is expected to have a lifetime of about 300 years. The results suggest that methane is occasionally produced or vented near the crater, which is near the Martian equator, they added.

NASA originally chose Gale Crater, which has a mountain in the middle of it, as a landing site for the rover because there were signs of water in the area. The crater is believed to have formed with a meteor hit Mars in its early history, about 3.5 to 3.8 billion years ago.

The announcement comes just weeks after another report concluding that a Martian meteorite called Tissint contains organic molecules of possible biological origin.